Some players like to record on their scorecards an expected number of matchpoints or percentage on each board as they play them.
In the early rounds, you will base your estimate largely on general bridge knowledge and the difficulty or otherwise of achieving the result.
As the rounds progress, the other scores on the traveller will play a greater part in the estimate.
Different methods are in use for estimating your score. Some players score on a scale of 0-4; 0 for a bottom, 1 for average minus, 2 for average, 3 for average plus and 4 for a top. Others use a scale of 1-10.
One advantage of estimating your score is that towards the end of the event, if you think your score is not good enough, you can vary your tactics to obtain abnormal scores. Another advantage is that knowing your estimated score can highlight any scoring errors.
For example, if you think you have had a 55% session and the posted score shows you with 50%, it may be worth your while to check the scores very carefully for possible errors.